The GRC-109 is the Army
adoption of the RS-1, and consists of receiver R-1004, transmitter
T-784, and power supply PP-2685 or PP-2684. The RS-1 and GRC-109 are
identical except for labeling, although all known T-784's have a
connector for a Burst Coder (GRA-71) on the front panel. This
difference is an "MWO" (Modification Work Order) on the
T-784. Other than the burst-coder connector and the markings, the
GRC-109 is virtually identical to the RS-1.

The T-784 characteristics
are described in NSN 5820-00-892-0880. Original cost: $532. The
R-1004 characteristics are described in NSN 5820-00-892-0882.
Original cost: $1122. The units are waterproofed and tested for 7.5
PSI.

There is also a GRC-109A
set, which is a later model and has a different case with hasp-type
lid fasteners, instead of thumbscrews; and there is a carrying handle
built into one side. It also has some cost-saving design changes: for
example, the window for the tuning dial is a part of the front-panel
casting, instead of being a separate screw-on piece. The "A"
model is probably more rugged, due to the thicker case and heavier
construction, but it is 'less attractive' than the earlier model. The
CIA did not have an equivalent to the GRC-109A, and production of the
RS-1 had probably stopped several years before.

A GRC-109 set
in use in the field, from a picture in the manual. See the RS-1
section for close-ups of the receiver and transmitter.

AN/GRC-109
Radio Station Specifications

Receiver
R-1004

Transmitter
T-784

Power
Supply PP-2684 and PP-2685

Weight

10
lbs

9
lbs

PP-2684:
24 1/2 lbs

PP-2685:
12 lbs

Dimensions

8-5/8"
X 5-1/2" X 5-7/16"

8-5/8"
X 5-1/2" X 5-7/16"

PP-2684:
10" X 8-1/2" X 5-1/2"

PP-2685:
8-5/8" X 5-1/2" X 5-7/16"

Tube
complement

1T4
RF amp

6AC7
oscillator

0B2
regulator

1L6
converter

2E26
final

1T4
IF amp (two)

1U5
detector/audio

1T4
BFO/audio

Frequency
Bands

3-6,
6-12, 12-24 MC

3-5.5,
6-9, 10-16, 17-22 MC

Power
Output

30
mW into 4K ohms

12-15
W, 3-15 MC

10-12
W, 15-22 MC

GRC-109 sets
with hand-crank generators, part of a static display in Germany in
1959. Image courtesy of Rocky Lewis (the gentleman in the picture).

The
"A-model" receiver, an R-1004A/GRC-109A serial 141A. Note
the lid fastener latches, and the tuning dial window that is integral
with the front panel. Internal components appear to be identical to
the R-1004.

GRC-109A
set. Image courtesy of Don Valentine.

Admiral Corporation
apparently made all of the GRC-109 equipment (and most of the
RS-1's), and Oklahoma Aerotronics made all of the GRC-109A's. The "A"
models all have an A-suffix on the serial number, and they have
snap-type lid fasteners instead of thumbscrews.

All (?) T-784's have been
modified as per "MWO 11-5820-474-35/1", which is described
in the GRA-71 manual as: "Modification of Radio Set AN/GRC-109
to make it compatible with Coder - Burst Transmission Group
AN/GRA-71". Presumably, this MWO was to install the connector on
the T-784 that mates with the GRA-71. The "A" models have
the burst-coder connector without the need for the MWO. Some (all?)
R-1004A's have the word "receiver" spelled incorrectly on
the lid's ID plate (they spelled it "reciever").

A
PP-2684/GRC-109 power supply. It is identical to the RP-1 except for
the ID plate. It accepts either AC input, or 6 volts DC from a
storage battery, or several voltages from a hand-crank generator
(using the capped connector in the lower-right). Author's collection.

A
PP-2685/GRC-109 power supply. It is identical to the RP-2 except for
the ID plate. It accepts AC voltage input only. The cap in the
lower-right is for access to the 0B2 regulator tube. Author's
collection.

Another power supply option
for the GRC-109 was the UGP-12 gas generator. It is a 2-stroke engine
that provided 115 VAC 400 Hz 125 watts. The UGP-12 is mentioned on
page 9 of the GRC-109 manual. Click herefor a picture (photo courtesy
of Pasquale Lombardi).

Yet another, probably later
power supply option is the PA-109, a switching-type supply for
operation from 12 VDC. It does not have military markings, but is
clearly intended to operate the GRC-109 set or it's equivalent.

A "Power
Adaptor PA-109", for operation from 12 VDC. Since the switch is
labeled "XMTR PWR", perhaps the receiver power is available
at all times? Note that the lid thumbscrews and the power connectors
are extremely similar to the GRC-109. The unit's weight is about 2
pounds. Image courtesy of Tony Grogan.

The data plate
from a PA-109. Image courtesy of Tony Grogan.

History
of the GRC-109

[See the similar historical
information under the RS-1 section.]

The GRC-109 started
production about 1961. Compared to the RS-1, GRC-109 units have more
date-coded components, and more documentation is available to support
those dates. GRC-109A units have a 1969 contract date on the ID
plate.

In late 1961, the CIA
organized a number of 12-man Special Forces teams to work with
Montagnard tribesmen, and used the RS-1 for communications.
Meanwhile, the Army's chief signal officer arranged for the RS-1 to
be adopted for military use and renamed the GRC-109. Even though the
Army had many RS-1 sets in use already, giving it an Army identifier
would have simplified logistics. By late 1962, the Special Forces
team network had 24 stations. The GRC-109 set in each "A
detachment" SF camp was kept in a sandbagged bunker, with
several antennas installed. The antennas were a target of Viet Cong
raids, but for emergencies, they found that a longwire buried 18"
underground in bamboo pipes could be used. [Ref. 6]

The GRC-109 became a
standard issue radio to all combat units in forward areas after 1965.
It was included in the inventory of all fire bases, and was at least
used as a backup radio. Even though Special Forces had access to the
latest high-tech radios, by the mid-1970's many units had adopted the
GRC-109 as their primary long-range radio. It was rugged, reliable,
and maintainable in the field, and offered several power supply
options. The newer radios tended to require specialized batteries
which were often not available in the field.

[Regarding
reliability:] I never had a 109 fail to function. I was always able
to communicate and send my traffic through with it. I operated in
many different locations, including an A camp in Viet Nam, the
forests in southern Germany, and out of apartment buildings in
downtown West Berlin.

[Regarding
the apartment building use:] I used the big power supply that is part
of the GRC-109 kit [PP-2684]. The antenna was a broomstick with about
50-75 feet of wire wound on it, with another 10 feet trailing off the
end. The coil of wire sort of made the antenna look electrically
longer. I placed the broomstick in a window and let the wire dangle
out of it. Other guys have used stairwell banisters for antennas. For
a ground I just ran a wire to the radiator in the room (most old
German pre-war apartments had steam heat).

GRC-109 notes from Don
Valentine:

We
had small dry batteries for the AN/GRC-109 receiver so we wouldn't
have to crank that %$#@%$# generator to send and receive messages. I
never saw a PA-109 while I was in SF. Apparently, it was only for
transmitting and the operator had to have a dry cell battery for the
receiver or have the team gorilla crank that &%$@#$ generator.

The
109 was very forgiving if you didn't erect a by-the-book antenna.
When in Laos, I communicated from Luang Prabang to Vietiane using a
coat hanger. It would even load a military vehicle, wire clothes
line, or barbwire fence and use that for an antenna.

The
AN/PRC-74 replaced the GRC-109 on the SFODs in the mid-60s, except
for the A Camps in Vietnam. We helped test the proto-types while we
were assigned to Project Delta [Det. B-52, 5th SFGA] in Vietnam. The
proto-types were called HC-162s.

SSG Robert
Kaszer, US Army Special Forces, using a GRC-109 set in 1962,
somewhere in southern Laos, either Paksane or Savannahkhet. Note the
use of a separate hand key. The headset appears to be an HS-30. Image
courtesy of Don Valentine.

SSG Homer Rice,
US Army Special Forces. Ban Houie Sai, Laos, 1962. Homer is setting
up the AN/GRC-109 Radio Set on a large piece of squared timber near
the boat ramp while thousands of local civilians are trying to flee
across the Mekong to Thailand to escape the advancing communist
Laotian and North Vietnamese troops. Image courtesy of Don Valentine.

SFC Edmundson,
US Army Special Forces. Ban Phoung, Laos, May 1962. Small outpost
65km east of Ban Houie Sai, Laos on Nam Tha Road. Lead element of
5,000 communist force over ran it the next day. Radio Set is on the
porch of the elevated thatched hut, in the shadows. We were just
arriving to relieve this Field Training Team and their radio operator
is on the porch by the 109 radio set. Image courtesy of Don
Valentine.

Image
courtesy of Rick Larson.

Pictured
above is an antenna device that was perhaps intended to be used with
the GRC-109. Details from Rick Larson:

"It
was intended to be fired in an M79 grenade launcher. The projectile
is a black anodized aluminum cylinder filled with green plastic
insulated antenna wire that pays out in flight. One end of the wire
was attached to the heavy steel cartridge case and the other in the
projectile. When the cartridge is fired, the projectile was supposed
to penetrate through the jungle canopy and leave the wire hanging in
the treetops. The other end remained attached to the fired case, and
when unloaded from the M79, could be cut off and attached to the
radio.I've seen three of these over the years and the one in my
collection is marked (in felt pen) for SEAL and SF use with GRC-103
radio. I believe this is incorrect and was actually intended for the
GRC-109. One example I've examined was a cutaway that came from the
manufacturer, AAI Corp., via a retired engineer. The other was at the
EOD unit at Camp Pendelton about 20 years ago."